In surgery, energy-based tissue sealing devices are used in procedures such as laparoscopy to haemostatically seal blood vessels and arteries. Such devices, otherwise known as tissue-bonding, or tissue-welding devices apply heat to a tissue region in order to induce tissue transformations such as the denaturation of proteins, the dehydration of tissue, and to alter collagen bonds. Energy is typically delivered to the tissue region in the form of Radio Frequency (RF) or High Frequency RF by electrodes that contact the tissue, for example in a clamping device such as the Ligasure™ marketed by the Covidien corporation. Other devices envisage to deliver energy to tissue regions in the form of optical or thermal energy. Tissue sealing may also occur to some extent on the remaining tissue following an intervention with an energy-based tissue cutting device.
Since tissue composition can vary significantly between different patients and in different parts of the body, adaptation of the tissue sealing or tissue cutting device settings is typically necessary during the sealing or cutting process respectively in order to obtain the best possible seal. At present the thermal and electrical impedance of the tissue are used as feedback signals to control the RF settings of the device. However, these parameters typically provide only partial information about the tissue, which limits the benefits offered by such feedback.
U.S. Pat. No. 5,762,609 relates to the use of optical feedback in such surgical tools, wherein it is disclosed to determine a tissue state dynamically during surgical interventions in a tissue welding device. U.S. Pat. No. 5,762,609 discloses to measure optical transmittance at specific wavelengths, and to measure optical parameters such as absorbance, scattering, anisotropy factor, elastic scattering, polarisation and fluorescence. The determination of specific tissue states is suggested as being possible using such data through empirical analysis and techniques such as class analysis and partial components regression.
In order to address the drawbacks of the above techniques and systems, the present invention seeks to improve the reliability of a tissue seal formed during a tissue sealing or tissue cutting process.